1. Field of the Invention
The present invention relates to a temperature control system for refrigerator, and particularly to a refrigerator temperature control system in which a compressor for compressing a refrigerant is driven at a speed variable between normal (lower) and higher rotational speed.
2. Description of the Prior Art
Generally, the inner temperature of a refrigerator, e.g. the temperature of its freezer or fresh food compartment, gradually rises due to frequent opening of the door of any compartment and loading therein of foods or the like, and hence the compressor is automatically driven periodically at predetermined time intervals so that the inner temperature of the refrigerator does not exceed a predetermined level. Nevertheless, the temperature of the freezer compartment or the fresh food compartment may rise beyond the predetermined temperature level depending on the frequency of door opening or the temperature or volume of foods newly loaded therein. In the conventional refrigerators, therefore, when the temperature of the freezer compartment or the fresh food compartment rises beyond a predetermined value, the compressor is forcibly driven for non-stop operation until the temperature is reduced below the predetermined temperature level.
Further, in a refrigerator comprising speed control means for changing the rotational speed of the compressor, when the internal temperature of the refrigerator rises higher than a predetermined level, the compressor is immediately driven at high speed so that the internal temperature is rapidly reduced thereby to maintain the temperature below the predetermined level.
A refrigerator of this type is disclosed in Japanese Patent Publication No. JP-A-60-71876.
In these conventional refrigerators, the compressor is driven at a rated or higher speed immediately when the internal temperature of the refrigerator rises beyond a predetermined temperature level.
In the case where the internal temperature thereof temporarily exceeds a predetermined level by opening the door of the refrigerator for a short time interval or by loading a small amount of foods in the refrigerator, however, the internal temperature is restored to the predetermined level within a short length of time by a refrigeration capacity of the contents loaded in the refrigerator.
It is, therefore, not necessary to forcibly operate the compressor continuously or at high speed in such a case. Nevertheless, the conventional control devices effect the continuous or high-speed operation of the compressor, resulting in a problem of an increased power consumption or noises.